1. FIELD OF THE INVENTION
The present invention relates to a device for controlling the guide vanes of the distributor of hydraulic machines and more particularly to the connection between the guide vanes and the member for controlling their orientation.
2. History of the Related Art
It will be recalled that a distributor of the above type is constituted by a variable number of guide vanes or blades sectioned like aircraft wings and associated with a slewable journal so that the assembly thereof is actuated synchronously by the common control member mentioned above. The latter is generally a gating ring which homogeneously varies the angle of inclination of the guide vanes. The guide vanes serve to supply water to a wheel over the whole of its periphery, as is well known in the art. The variation of the angle of inclination of the guide vanes causes a change in the admission flowrate of the water and varies the approach angle on the wheel. This assembly is governed by the speed regulator which maintains the unit at the speed of synchronism whatever the flowrate and pressure head.
The present arrangement of such a distributor device includes a system of connecting rods and cranks actuated by the control member, which system acts on a lever fitted angularly on the journal of the guide vane.
In the event of effort upon closure of the distributor, for example when an obstacle slips between two guide vanes, any manoeuvring effort is transferred onto the blocked guide vane. A fusible or break element has therefore been provided which avoids overcouples which might in that case damage the distributor.
In the event of break of the element in question, an out-of-step of the corresponding guide vane is produced, with the result that the supply of the hydraulic machine is disturbed. Manual intervention is then necessary, i.e. at the gating ring to change the fusible element.
In order partially to overcome this drawback, FR-B-1354691 for example teaches producing the lever in two parts and joining these two parts by an elastic element. However, although this system is satisfactory for small efforts, it does not prevent the use of a fusible element which breaks under high efforts.